Radio frequency identification systems (“RFID”) are frequently utilized in many applications, such as electronic surveillance and inventory tracking. RFID systems typically consist of a data carrier, such as a tag or transponder, and a reader. The tags or transponders are used in various formats, such as disks, smart cards, plastic housings, or in paper-thin tags. The tags consist of a silicon die attached to the contact pads on the antenna. Anisotropic or isotropic conductive pastes, anisotropic conductive films and non-conductive pastes are utilized to attach the antenna to the die. To attach the silicone chip to the antenna, manufacturers frequently utilize semiconductor flip chip technology processes. Via the flip chip process, the radio frequency identification dies are picked and placed onto the antenna after an anisotropic conductive adhesive is applied to the pads. The adhesive is then cured at a high temperature for a short time while pressure is applied on top of the die to ensure electrical connection. Due to a number of variables, the flip chip process often has the drawback of a relatively slow processing speed
In all of the existing processes for assembling RFID systems adhesives are applied in a liquid or film form immediately before the die is attached to the antenna after which the unit is cured via heat or energy radiation. Numerous difficulties are presented by the use of such adhesives. For example, the die are extremely small and usually only a few millimeters square in size. Thus, the distances between the attachment bumps on the die are too small to utilize isotropic conductive paste.
Die straps which allow for high speed reel-to-reel processing of the interconnection between the die and the antenna may be utilized. Such high speed processing is critical to manufacturers in order to produce the extremely large number of tags utilized in various industries. The use of high speed processing poses a number of difficulties for manufacturers. For example, high speed processing limits the type of adhesive application techniques and the type of adhesive that may be utilized. A low viscosity adhesive is required for high speed adhesive deposition. However, a low viscosity adhesive tends to have low green strength. Low green strength may cause the die to short after placement on the antenna pads because of the vibration experienced during high web processing speeds. Further, as adhesive has a limited work life, there will be a limited time during which the adhesive may be applied without a variation in its viscosity. To avoid the variation, manufacturers are required to interrupt the assembly process to insert fresh conductive adhesive, resulting in an inefficient process having downtime. It would be advantageous to provide an RFID antenna that could be readily utilized in a high speed assembly process along with a method for assembling RFID systems at a high speed.